In the construction industry it is often necessary to create multiple accurate datum level/points in all areas for all buildings being constructed or renovated. Creating these datum points at various locations on columns or walls enables a builder to ensure his/her infrastructure work is sufficiently level, and to relate it to the building datum heights established by the Architect. It also enables other traders to correctly install their works so that gaps between, for example, false ceilings, floors, windows, plumbing, electrics and inbuilt furniture are accurate. It is also often necessary to determine an individual datum level accurately between two points, for example across a room or window or door opening, or a datum point between a series of columns cast in a particular area.
Laser technology has been adapted to carry out the type of leveling work described above and is now widely used for this purpose. Lasers substantially reduce the time and effort required to create datum points when compared to the traditional methods.
However, a laser level in itself has no means of defining whether its light path, or line of collimation, is actually horizontal. The traditional leveling technology has therefore to be combined with laser light technology. For example, a laser generating light can be attached to a spirit level to enable the user to point the laser light, for example, across a gap. However to make the spirit level horizontal requires the operator to move one end of the level up or down until the bubble in the radiused glass vial is centered. If a level datum is required on each side of a gap and the gap is too wide for the operator of the level to reach by hand, the operator will summon an assistant to mark the distant point across the room, even though the operator holding the level can see the point where he/she requires the datum mark to be made.
An alternative system, which achieves greater accuracy, is also available for performing the leveling work. Here, a laser light mechanism is retained in a box and suspended in a pendulum which can rotate freely when the laser box is + or −5° to the vertical. The continuous swinging action of the pendulum is damped by passing the base of the pendulum through a magnetic field. The pendulum comes to rest very quickly and the subsequent laser ray defines a precise horizontal light path on the collimation line of the instrument, centered near or at the pivot point of the pendulum, and at a normal to the gravitational vertical line of the pendulum. Modern laser levels can define a dot of light or a short horizontal line or a continuous line subscribing 360°. To create a series of level points around a room the operator sets the laser box onto a dedicated tripod placed in the middle of the room, switches the laser on, ensuring the level is sufficiently upright to allow the pendulum to swing, and then walks around the room marking level datum points at locations where they are required. Whilst this operation only requires one operator, the valuable laser level on the tripod is left unattended and could possibly be inadvertently knocked over by other building tradesman.
At other times it is necessary to relate the collimation line of sight of the laser level with a known main datum level point, marked on a vertical surface and defined on a building drawing, and then to transfer the height of this known main datum point around an area to enable building tradesman to directly relate their works to the known main datum point. The difficulty with the traditional technique of using a laser level mounted on a tripod to transfer the height of this known main datum is that it is virtually impossible to set the height of the tripod and thus the height of the laser level such that the line of collimation of the laser level coincides exactly with a main datum. This means that the difference in height between the line of collimation of the level viewed at the location of the main datum and the main datum itself has to be measured and then added or subtracted from the main datum height in order to calculate the precise height of the line of collimation of the level. Invariably this will necessitate the time consuming use of a calculator or pen and paper and, once again, whilst this operation only requires one operator, the valuable laser level on the tripod is left unattended and could possibly be inadvertently knocked over by other building tradesman.